[STATSGRASS] different kriging results with the same parameters

[Edzer J. Pebesma]

My only thought is try increasing the nugget variance; the Gaussian 
variogram model always triggers some kind of alarm. Still, output 
shouldn't vary.

Have you tried replacing srtm$band1~1 with band1~1 (in which case it is 
taken from the second argument, srtm2)? Something like

krige(band1 ~ 1, srtm2, mask_SG, model=vrg.eye, maxdist=250);
--
Edzer

Carlos "Guâno" Grohmann wrote:
> I was kriging some SRTM DEMs, and I noticed that I get different
> results with the same parameters!!
> check out:
>
> summary(srtm) - original data
> Data attributes:
>     band1
> Min.   : 634.0
> 1st Qu.: 759.0
> Median : 814.0
> Mean   : 856.5
> 3rd Qu.: 923.0
> Max.   :1312.0
>
> vrg.eye<-(vgm(psill=950, model="Gau", range=245, nugget=6.2));
>
> OK_pred_md250 <- krige(srtm$band1 ~ 1, loc=srtm2, newdata=mask_SG,
> model=vrg.eye, maxdist=250);
>
>
> summary(OK_pred_md250);
> Data attributes:
>   var1.pred         var1.var
> Min.   : 632.8   Min.   :  8.054
> 1st Qu.: 759.2   1st Qu.:  8.576
> Median : 814.3   Median :  8.712
> Mean   : 856.4   Mean   :  9.052
> 3rd Qu.: 923.6   3rd Qu.:  8.865
> Max.   :1307.6   Max.   :395.609
>
> Data attributes:
>   var1.pred         var1.var
> Min.   : 632.4   Min.   :  8.040
> 1st Qu.: 759.2   1st Qu.:  8.577
> Median : 814.3   Median :  8.711
> Mean   : 856.4   Mean   :  9.048
> 3rd Qu.: 923.6   3rd Qu.:  8.863
> Max.   :1306.2   Max.   :341.567
>
> Data attributes:
>   var1.pred         var1.var
> Min.   : 632.9   Min.   :  8.039
> 1st Qu.: 759.2   1st Qu.:  8.576
> Median : 814.3   Median :  8.712
> Mean   : 856.4   Mean   :  9.052
> 3rd Qu.: 923.6   3rd Qu.:  8.865
> Max.   :1306.9   Max.   :345.084
>>
>
>
> So, the minimum and maximum have changed each time. Why?
>
> thanks
>